Posts Tagged resistivity

Practical Inversion for Geoscientists

Posted by on Wednesday, 10 April, 2013
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A short course on the why, how, and what of geophysical inversion

Presented by the B.C. Geophysical Society

This is a 2-day workshop consisting of 1 day of lectures (April 24th) followed by a 1 day hands-on workshop (either April 25th or 26th). Delegates can register for just the lectures or both the lectures and workshop.

Registration available until April 15th at: www.bcgsonline.org

Date: April 24th – 26th 2013

Address: SFU Downtown Campus; Vancouver BC

Registration: Registration is now open!  Please fill out attached pdf form (link below) and click submit.  Registration will be complete once payment is made via Paypal link.  Delegates are asked to choose one workshop day among April 25th or 26th.

Day 1 – Introduction to inversion
– Introduction to inversion in exploration

Reasons for doing inversion
Range of inversion options: magnetics, gravity, EM, IP-resistivity, seismic
Fitting geology and data

– Background on inversion

Unconstrained/constrained
Joint and collaborative
The future of inversion

– Before inversion – forward modeling

forward modeling
petrophysics drives the story
complexity vs. adequacy

– Case studies

Potential fields
EM
IP-resistivity

Day 2 – Workshop with Case studies
Multi-disciplinary teams will use geological, geophysical and geochemical data from two deposits (Babine Lake porphyry Cu-Mo, BC and Minto Cu, YK) to develop exploration targets. Teams will present their evaluations of the data to stimulate group discussion.

Inversion results for the available geophysical surveys will be presented to demonstrate state-of-the-art technology and best practices.
Sponsors for the short course are currently being solicited. Please contact Victoria Sterritt at Victoria.Sterritt@teck.com for details. Proceeds go to the KEGS Foundation.
For those interested in more information about the short course, please email info@bcgsonline.org


Electrical Resistivity/IP/SP for Environmental and Engineering Applications

Posted by on Friday, 18 January, 2013

Pennsylvania Council of Professional Geologists announces Resistivity/IP/SP for Environmental and Engineering Applications Short Course on February 27, 2013 in Harrisburg, PA. The course instructor will be Brad Carr, Ph.D (formerly of AGI). This 1-day short course will cover DC Resistivity, IP, and SP topics such as: theory; data acquisition; field procedures; data processing; data presentation; and interpretation. The course will also provide attendees a better understanding of the strengths of 1D, 2D, 3D and 4D resistivity/IP imaging and SP monitoring methods through the discussion of various case histories, survey design, forward modeling and inversion and the use of data processing/analysis software as applied to surface, borehole, marine and time-lapse monitoring data.

Overview

Electrical Resistivity/IP/SP for Environmental and Engineering Applications is designed for professionals who are involved in, beginning to consider, or have oversight/review responsibilities of others currently conducting DC Resistivity, IP or SP surveys on engineering or geotechnical projects.

This 1-day short course will cover DC Resistivity, IP, and SP topics such as: theory; data acquisition; field procedures; data processing; data presentation; and interpretation. The course will also provide attendees a better understanding of the strengths of 1D, 2D, 3D and 4D resistivity/IP imaging and SP monitoring methods through the discussion of various case histories, survey design, forward modeling and inversion and the use of data processing/analysis software as applied to surface, borehole, marine and time-lapse monitoring data.

Details..


Large IP Anomaly at Baffin Island Gold Property

Posted by on Friday, 3 February, 2012

Commander Resources Ltd. announces that results from the deep sensing, 3-D Induced Polarization (IP) Survey conducted at the Kanosak gold prospect in the 2011 field season have been reported. The survey results indicate the presence of a steeply dipping, cross-cutting zone of high chargeability and low resistivity below gold anomalous strata bound sulphide mineralization hosted in flat lying sediments over a 3 km strike length. The IP anomaly is interpreted as a possible feeder to the extensive surface mineralization. Trenching and shallow drilling has previously found widespread free gold in quartz veins and associated with disseminated arsenopyrite and pyrite.

The survey was conducted by Abitibi Geophysics of Val d’Or, Quebec, who also prepared all plans and interpreted the results. The report states that a large, sub-vertical anomaly commences about 150 metres directly below the surface gold showings at Kanosak. The IP chargeability anomaly underlies the entire 3 km strike extent of the grid. Additionally, the anomaly is open to the south, with the strongest response at the southern most grid line.

The report states that the intensity of the anomaly increases with depth, with primarily background chargeability values (15-30 mv/V) from surface to 50 metres, increasing to some of the highest recorded values (300 mv/V) at 150 metres. The high values are interpreted to be attributable to sulphides, as there is no graphite recorded in this area.

The IP results are presented with maps on the Company’s website. Three plan maps show chargeability values at 50-100-150 metre depths and a surface interpretive plan shows the IP anomaly, along with completed and proposed drill holes. Most of the holes (shown in grey) were drilled west of the target or were too shallow to reach the top of the interpreted source. This previous drilling was designed to test surface gold showings and early stage, shallow (less than 75 metre depth) IP response. Proposed holes, (shown in green) are designed to test the new, deep responses.

The interpretation of the IP response from the deep, 3-D survey indicates that a very large, strong disseminated sulphide source dips sub-vertically below 150 metres depth from surface. This may be the feeder system which produced the very high grade, but irregularly distributed gold veins scattered over 3 km’s on surface at Kanosak.

The chargeability anomaly is associated with a resistivity high, which is also reflected in the surface showings at Kanosak. Here, gold is associated with the arsenopyrite and minor pyrite, which are good IP sources. As the IP source is associated with magnetic lows, the source is not expected to be magnetic pyrrhotite or magnetite.

A 3,000 metre drill program has been proposed to test these strong, deep targets. A camp is established and permits are in place.


Geophysical Survey Results at La Vereda Concession in Colombia

Posted by on Friday, 3 February, 2012

CB Gold Inc.  provides summary geochemical and geophysical survey results from the La Vereda Concession at its Vetas Gold Project, District of Santander, Colombia (“Vetas Gold Project“), located 10km south of AUX’s La Bodega and La Mascota deposits. The 80% owned La Vereda property is covered by a concession contract expiring in 2037.

La Vereda Geophysics Survey Results:

The Company conducted an Induced Polarisation (“IP”) geophysical survey at La Vereda, identifying a major anomaly characterized by high chargeability and low resistivity (see attached 3-D images – additional plan view sections can be viewed at www.cbgoldinc.com). Surface mapping and geochemical sampling had identified quartz veining and stock work zones similar to other properties at the Vetas Gold Project.

The geophysics anomaly at La Vereda is approximately 2,000 meters long and up to 700 meters wide and is interpreted as an extension of the epithermal style mineralization found at surface, with the high chargeability indicating the presence of potential sulphide mineralization at depth. The anomaly strikes northeast / southwest, similar to many mineralized structures in the Vetas – California District.

Mapping to the north of the property boundary has identified an outcropping zone of quartz veins, approximately 400-500 metres wide, that strikes northeast and projects under cover directly into the geophysical anomaly identified at La Vereda. Summary results from surface channel samples across this vein cluster include gold grades up to 26.3 g/t Au (Additional geochemical results can be viewed at www.cbgoldinc.com). Drilling will target potential mineralization with up to 10 initial holes planned into the main zones identified by the survey upon receipt of drilling permits.

La Vereda Geochemistry:

All the samples taken by CB Gold at its La Vereda Concession were analyzed by ALS Chemex Labs in Lima, Peru. The Company has a standard QA/QC program which includes blank material, certified reference material and duplicate samples. The QA/QC program has been reviewed by various independent consultants experienced in QA/QC work.

Fabio Capponi, Chief Executive Officer, noted “The results of the exploration work at La Vereda show the potential of this property to be an exciting additional target for the Company and we plan to commence drilling as soon as possible to test the extensive geophysical anomaly”.


IP/Resistivity Survey at Copper-Gold-Silver Project in Turkey

Posted by on Sunday, 2 October, 2011

Empire Mining Corporation announces that an IP/resistivity survey has commenced at the newly identified Southwest Zone of the Demirtepe copper-gold-silver and molybdenum project in Turkey, with the aim of identifying the possible location of the source porphyry system that is believed to be the driver for the skarn-hosted mineralization at Demirtepe.

A total of 20 line kilometres is planned to cover an area of 3.5 km2 in nine east-west and one north-south profile each about 2.0 km long. Time-domain dipole-dipole surveying will be used with a six dipole array, with line spacing of 200 metres. A map is available at the following link:

http://www.empireminingcorp.com/i/nr/2011-08-28-geochem-IP.pdf

Recent sampling at the Southwest Zone has identified a continuous copper-gold anomaly currently about 1.8 km long and up to 800 metres wide and still open to the southwest; with elevated copper levels in soils broadly coincident with elevated gold. Rock sampling results include 4.68% copper, 5.58 gpt gold and 59.3 gpt silver from wollastonite bearing boulders and 3.2% copper in garnet skarn boulders with copper oxide staining.

The new Southwest Zone is located approx. 1 km to the southwest of the Main Zone where drilling by Empire has encountered significant grades and intervals of copper-gold-silver and molybdenum skarn mineralization, including the discovery hole which intersected 47.53 meters of 2.02% Copper, 0.96 g/t Gold and 21.64 g/t Silver, including 8 meters of 9.1% Copper, 4.68 g/t Gold and 95.3 g/t Silver.

The Southwest Zone is interpreted as having formed the basement below the Demirtepe Main Zone deposit which then became detached. This view is supported by higher temperature signs of epithermal style quartz with chalcopyrite and pyrite. The identification of a basal detachment fault at the bottom of the Main Zone led to the discovery of the Southwest Zone.

The next phase of drilling at Demirtepe will be focused on the Southwest Zone.


IP/resistivity survey at the Karapinar copper project in Turkey

Posted by on Thursday, 22 September, 2011

Empire Mining Corporation announces that an IP/resistivity survey has commenced at the Karapinar copper project to seek extensions to the chalcocite enrichment blanket identified in recent drilling, and to target higher grade primary porphyry and skarn mineralization to the north of the previously drilled area. A total of eight line kilometres are planned in four north-south profiles, each two kilometres long. Dipole-dipole surveying will be used with a six dipole array, with spacing of 200 metres. Empire plans to drill test any targets generated.

Recent drilling at Karapinar (see announcement of August 23, 2011) has intersected a 60 metre zone of chalcocite enrichment in hole KDH-018 grading 0.93% copper, 0.11 gpt gold and 0.017% molybdenum from a hole depth of 79.6 to 139.6 metres. KDH-018 is one of the easternmost holes drilled at Karapinar so far and has revealed significant expansion potential.

The secondary enrichment lies beneath a 48 metre zone of oxide mineralization grading 0.25% copper from a hole depth of 31.6 metres. The combined oxide and chalcocite mineralization grades 0.63% copper, 0.11 gpt gold and 0.01% molybdenum over 108 metres. Hole KDH-018 lies 90 metres northeast of hole KDH-008 and 100 metres southwest of KDH-007, both of which intercepted secondary copper mineralization in Empire’s 2008 drilling campaign.

The presence of a chalcocite blanket at Karapinar is unusual in Turkey, due to relatively rapid uplift and erosion, although a transition from oxide to sulphide has been noted in previous drill holes and characterised by a varied amounts of chalcopyrite, chalcocite, bornite, native copper and copper oxides which enhance the copper grade in the shallower sections of drill hole.

On a larger scale, the intrusive porphyry deposit possibly extends 1 km to the north, based on copper and molybdenum anomalies to the north and lead zinc in the dolomites north of the drilled porphyry. This carbonate mass is interpreted as a large roof pendant and one hole drilled by Rio Tinto in 2003 (KDH-005) penetrated through the marble and contact skarns and into porphyry.

Empire is also planning additional mapping and sampling at Karapinar, before the next phase of drilling.

Various Karapinar maps can be viewed at the following link:

http://www.empireminingcorp.com/i/nr/2011-09-21-maps.pdf


GEOPHYSICAL RESULTS: NEW EXPLORATION TARGETS AT KIZILTEPE

Posted by on Friday, 3 June, 2011

Ariana announced geophysical  test results from their Kisiltepe project in Turkey.

The programme has successfully confirmed the presence of several potential vein systems in the northern half of the prospect area.

Highlights

  • Several resistivity and chargeability anomalies, which may coincide with buried vein systems, located to the northeast of the Arzu South vein.
  • One significant new anomaly coincides directly with an area of extensive quartz vein float from which grades of up to 21.1 g/t Au have been recorded.
  • Significant additional exploration upside defined on the prospect.
  • Exploratory drilling programme to commence within days.

Dr. Kerim Sener, Managing Director, commented:

“These geophysical results coupled with systematic sampling have demonstrated the potential for further significant veins to be discovered at the Kiziltepe prospect.  These geophysical anomalies will be targeted by exploration drilling.  The first phase of this drilling is due to commence over the weekend (27/28 March) and its aim will be to confirm the presence of these buried vein systems or their associated alteration.  There is clear potential at the prospect to increase the current mineral resource and to further enhance the economics of the project.”

Geophysical Programme

The geophysical programme described here was undertaken over a 2km2 area covering the northern half of the Kiziltepe vein field in an area where no veins appear in surface outcrop.  Detailed mapping of the area had previously identified the potential for buried vein systems and sampling of one area of extensive quartz sub-crop outlined grades of up to 21.1 g/t Au in composite rock-chip sampling of float material.

Data was collected from nine northeast-southwest oriented Induced Polarisation (IP) / resistivity profiles, which were spaced 180-230m apart and designed to coincide directly with existing geochemical data lines (total length surveyed is approx. 12km).  A pole-dipole array was used with 30m or 60m electrode spacing, using a Zonge GGT-3 transmitter and a Scintrex IPR-12 receiver operating in the time domain.

Several high chargeability and high resistivity anomalies were identified in the two-dimensional inversion models, which are interpreted to coincide with zones containing vein systems and their related alteration.  Zones with resistivities greater than 150 Ohm.m, in places coinciding with chargeabilities less than 10mV/V, were identified as significant anomalies.

In plan, the distribution of the anomalies is broadly coincident along three distinct trends; one in the immediate vicinity of Arzu South (possibly representing a splay), another directly beneath a hill which conceals part of the Arzu structure and one in the vicinity of the Vein 5 structure.  These trends possibly represent new vein systems at depth, which must be tested by drilling.  An initial programme of drilling comprising several short test holes will be focused on certain of these areas.  No more than 1,000m of drilling is envisaged for this initial programme.

Figure 1 showing an inverse model resistivity (top) and chargeability (bottom) profiles on Line 2 viewed looking to the northeast.  Towards the left-hand side of the sections a resistive body is identified which possibly represents a north-south trending splay off the Arzu South structure.  Approximately midway along the section (just to the left of the 480 mark) is a distinct resistive body which corresponds directly with the area of quartz vein float from which several highly anomalous results were obtained in rock-chip sampling.  Towards the right-hand side (near the 960 mark) a resistive body is coincident with a discrete high chargeability anomaly and this does not correspond to any known vein system and represents a new target area for drilling.


VTEM Survey on Prospective Uranium Properties in Athabasca Basin

Posted by on Saturday, 23 April, 2011

Unity Energy Corp. announces that it has engaged Geotech Ltd. to conduct a heliborne VTEM geophysical survey over its Close Lake, Lampin Lake and Hoppy Lake Projects in the northeastern Athabasca Basin. VTEM is highly effective at locating discrete conductive anomalies, magnetic features extending to the basement and mapping lateral and vertical variations in resistivity and is a leading edge solution for uranium exploration in the basin. VTEM is an evolving technology and this latest generation boasts a higher sensitivity, achieved by noise reduction and optimization of transmitter current waveform along with dipole moment increases. The low noise level significantly extends conductance aperture and conductance discrimination. The survey will comprise of ~1300 line kilometers with 100m spacing and is expected to be completed within two weeks.

The Company was very impressed at the capability and resolution of the VTEM survey, which in 2010 helped to define three high priority targets at Unity’s Waterbury Lake Project, which is just ~10km south of the Midwest Mine and Hathor’s Roughrider Project. The Company is also in the process of finalizing arrangements for a ground resistivity survey of targets at Waterbury, which should commence in the near term.

Close Lake Project, which is comprised of a singe mineral disposition covering an area of ~596 hectares, is ~10.6km northwest of the Cigar Lake mine. The Tucker NE conductivity trend, which lies immediately north of the CL Property, was delineated by a 1991 Comega (now Areva) ground EM survey and a 2004 MEGATEM Airborne EM & Magnetic Survey. The anomaly was interpreted as a series of 3 or more northeast parallel basement conductive anomalies, the most southerly of which (C-12A) lies ~170m from the northernmost boundary of Unity’s CL property.

The Lampin Lake Project consists of a single 500 hectare disposition located on the eastern margin of the Athabascabasin.  The Property is 3.7km southeast of Unity’s Waterbury Lake Property and is bordered by claims held by Dennison to the east (Hidden Bay Project) and Cameco Corporation on all other side.

From 2004-2006, Cameco tested the northeast trending Q12 EM conductor series with ground geophysics and diamond drilling. EM and gravity surveys allowed for the interpretation of the Q12 fault, as well as numerous cross faults that extend onto the Lampin Lake Property. In addition, a northeast resistivity high, extending for ~750m along the southeastern edge of the Lampin Lake Property was defined by EM inversions.

In September 2002, UEX Corporation and Cameco Corporation commissioned a fixed-wing triaxial gradiometer aeromagnetic survey to cover the entire Hidden Bay and Rabbit Lake properties. Goldak Airborne Surveys of Saskatoon, Saskatchewan was contracted to carry out the survey and a total of 6,816 line kilometres of data was collected along 200 metre spaced flight lines. The data collected from this survey was combined with a project-scale EM conductor map to facilitate a regional geological and structural interpretation. Emphasis was placed on identifying the principal geological units, the most prominent structural features, and the areas most prospective for finding uranium mineralization.

The Hoppy Lake Property covers an area of 1924 hectares and is ~10km southwest of the Cigar Lake Mine.

In 2007, Condor Consulting completed an interpretation report for Dejour Enterprises/Titan Uranium and identified a number of Target Zones deemed worthy of follow-up. The report describes the processing and analysis of several VTEM airborne electromagnetic and magnetic surveys carried out for Dejour by Geotech from September-October 2006. The object of the survey was to explore for unconformity style uranium mineralization of both the Simple (Low Rare Earth Elements, (REE) basement-hosted) and the Complex (High Rare Earth Elements, (REE) sandstone-hosted) types.


Geophysics and overburden geochemical techniques are the best targeting tool

Posted by on Monday, 20 December, 2010

Orestone Mining Corp.  announces complete copper and gold assays from diamond drill hole 09-05 on its 41,000 hectare, 100% owned Captain Property in the Quesnel Terrane of central British Columbia. The drill core yielded assays of up to 0.65 grams per tonne gold and 0.22% copper. The Company reported, in a January 27, 2010 News Release, that the 137 metre vertical hole bottomed in a 3.1 metre interval averaging 0.34 g/T Au and 0.16% Cu. Geologists from the Company have now sampled the entire drill hole and received anomalous copper and gold assays from those samples.

As summarized in a table below, anomalous copper and gold occur in thicknesses up to 20 metres, but the center of the mineralizing system has likely not yet been encountered. This drill hole is adjacent to chargeability and resistivity anomalies resulting from a July 2010 induced polarization (IP) survey completed on the Property. There are also gold and copper anomalies from a recently completed soil survey that are coincident with the chargeability and resistivity features and reinforce new drill targets.

The Property lies immediately south of the Mt Milligan copper-gold project currently being constructed by Thompson Creek Metals Company Inc. There is variable glacial cover in this area, so geophysics and overburden geochemical techniques are the best targeting tools. Mt. Milligan and other alkalic copper-gold deposits in this region are associated with coincident magnetic and IP anomalies. The glacial overburden in drill hole 09-05 is approximately 45 metres deep.

The chargeability-resistivity-magnetic anomalies to the west of this drill hole are the best and largest copper-gold alkalic porphyry targets ever defined on the Property. Averages of copper and gold assays from approximate ten metre runs are provided in the table below. The data reveals a pronounced increasing gradient of both copper and gold from the top of bedrock to the bottom of the hole. The increasing grades with depth are encouraging as they indicate the potential for higher, potentially economic gold and copper grades at depth and laterally, adjacent to hole 09-05. Mineralization in the hole is hosted by a breccia with a matrix of fine-grained pyrite and chalcopyrite within andesitic volcanoclastic rocks. Overall pyrite content is about 3%.